Design of a Quadruple Band Metamaterial Absorber for Sensing in the Terahertz Region

This work proposed the design and analysis of a high performance quadruple band metamaterial absorber suitable for terahertz (THz) sensing applications. The unit cell of the structure is comprised of two concentric square metal rings placed on a polyimide substrate and a metal ground plane beneath them. The concept being considered here depends on the impedance matching between the absorber and the medium above it. The sensor can detect a wide range of refractive indices (1.0 - 1.6), covering most of the biosamples, and the use of multiband ensures high accuracy in the detection of analytes. The proposed design offers high sensing performance with a maximum sensitivity of 160, 240, 450, and 720 GHz/RIU and a maximum Q factor of 25.421, 26.738, 59.712, and 51.516, respectively, at its four resonant frequencies. The sensor is polarization insensitive which will have less complexity in the measurement setup. It is also capable of providing a maximum FOM of 8.421, 5.310, 14.803, and 14.145. The proposed structure's properties, including its high sensing performance, polarization insensitivity, and structural simplicity, contribute to its being an excellent candidate for THz biosensing applications.